Fuel Pump Relay

This procedure replaces the fuel pump relay, which controls power delivery to the fuel pump. This is a low-complexity electrical component replacement requiring no fuel system disassembly.

Warnings

Tools required

Parts

• Fuel pump relay × 1 — Honda 39794-TBA-A01 or equivalent

Preparation

1. Park vehicle on level ground and engage parking brake
2. Turn ignition to OFF position and remove key completely
3. Allow engine to cool if recently operated
4. Open hood and secure with prop rod
5. Locate negative battery terminal on driver side of engine bay
6. Using 10mm socket, loosen negative battery terminal clamp and disconnect cable. Secure away from terminal
7. Wait 3 minutes for electrical system to discharge
8. Locate the under-hood fuse/relay box on driver side near firewall (2016-2019) or under-dash fuse panel on driver side kick panel (2020-2021)
9. Consult owner's manual or fuse box cover diagram to identify fuel pump relay position (typically labeled PGM-FI MAIN RELAY #1 or FUEL PUMP)

Procedure

1. 1

   Access relay box
   For under-hood location: Press release tabs on sides of fuse box cover and lift off. For under-dash location: Remove lower kick panel by pulling outward on clip fasteners, then open fuse panel door. Set covers aside in clean location.
2. 2

   Document relay location and orientation
   Using your phone camera or diagram, document the exact position and orientation of the fuel pump relay before removal. Note the terminal numbering on the relay base (typically terminals 1-5). Verify you have identified the correct relay by checking fuse box diagram - do NOT remove random relays.
3. 3

   Test existing relay (optional diagnostic step)
   If you have a multimeter and want to verify relay failure: With relay still installed and battery connected, have helper turn ignition to ON (engine off). Use multimeter to check for 12V at relay terminals 3 and 5 (power supply). If no power present, check fuses first. Listen for relay click when ignition turned on. No click may indicate coil failure.
4. 4

   Remove fuel pump relay
   Grip relay firmly and pull straight upward with steady even pressure. If relay is stuck, use relay puller tool or gently rock side-to-side while pulling up. Do NOT use excessive force or pry tools that could damage socket terminals. Inspect removed relay for signs of burning, melted plastic, or corroded terminals.
5. 5

   Inspect relay socket
   Using flashlight, inspect the relay socket terminals for corrosion, burning, discoloration, or bent pins. Check for moisture or debris inside socket. If socket shows heat damage or severe corrosion, the socket itself must be replaced - relay replacement alone will not solve the problem. Verify all socket terminals are present and properly seated.
   ⚠A damaged or corroded socket will cause premature failure of the new relay. If socket damage is present, professional repair of the fuse box may be required.
6. 6

   Clean socket terminals (if needed)
   If minor corrosion is present on socket terminals, spray with electrical contact cleaner and allow to dry completely (2-3 minutes). Do NOT use sandpaper or abrasive materials on socket terminals. For heavy corrosion, socket replacement is required.
7. 7

   Verify new relay specifications
   Compare new relay to old relay. Verify identical terminal configuration, identical part number or verified cross-reference, and same voltage/amperage ratings printed on relay body. Honda fuel pump relays are typically 12V, 30-40A rated. Using incorrect relay can cause immediate failure or fire.
8. 8

   Install new fuel pump relay
   Align new relay terminals with socket holes, ensuring correct orientation matching your documentation from Step 2. Relay will only fit one way - do NOT force. Press relay firmly into socket until it seats completely flush with surrounding relays. Relay should be secure with no wobble or raised edges.
9. 9

   Reinstall relay box cover
   Position relay box cover and press down firmly until all tabs click into place. Ensure cover is fully seated and diagram is readable. For under-dash location, close fuse panel door and reinstall kick panel by pressing clip fasteners into position.
10. 10

    Reconnect battery
    Reconnect negative battery terminal to battery post. Tighten 10mm terminal clamp bolt to secure connection - should be tight enough that cable cannot rotate on terminal.

Reassembly

1. Ensure all fuse box covers are fully secured and properly latched
2. Ensure no tools or parts are left in engine bay
3. Close hood and verify it latches properly

Verification

• Turn ignition to ON position (do not start engine). Listen for fuel pump priming sound from rear of vehicle - should run for 2-3 seconds. This confirms relay is energizing pump.
• Check instrument cluster for check engine light, fuel system warnings, or error messages. None should appear.
• Start engine and verify normal starting behavior with no extended cranking
• Allow engine to idle for 1-2 minutes and verify smooth operation with no stumbling or misfires
• Turn engine off, wait 10 seconds, and restart to verify consistent operation
• Test drive vehicle in safe area to verify normal acceleration and no fuel delivery issues under load
• If problems persist after relay replacement, diagnose fuel pump, fuel pump fuse (typically 15A in under-hood box), wiring harness, or ECM control circuit - relay may not have been the root cause

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